HomeMy WebLinkAboutFOOTHILLS UNITARIAN CHURCH EXPANSION - MJA210002 - DOCUMENT MARKUPS - ROUND 2 - DRAINAGE REPORT
PREPARED FOR:
FOOTHILLS UNITARIAN CHURCH
1815 YORKTOIWN AVENUE,
SECTION 22, TOWNSHIP 7 NORTH,
RANGE 69 WEST OF THE 6th PRINCIPAL MERIDIAN
LARIMER COUNTY, COLORADO
FINAL
DRAINAGE
&
EROSION CONTROL
REPORT
PREPARED BY:
BASELINE ENGINEERING CORPORATION
1950 FORD STREET
GOLDEN, CO 80401
June 18, 2021
JOB # CO3355
2
ENGINEER CERTIFICATION
“This report (plan) for the Final Drainage and Erosion Control Report for the “Foothills
Unitarian Church,” was prepared by me (or under my direct supervision) in accordance with
the provisions of the Fort Collins Stormwater Criteria Manual and was designed to comply with
the provisions thereof. I understand that the City of Fort Collins does not and will not assume
liability for drainage facilities designed by others.”
_______________________________________________
Noah J. Nemmers
Registered Professional Engineer
State of Colorado No. 39820
OWNER CERTIFICATION
“(Owner/Applicant) hereby certifies that the drainage facilities for the “Foothills Unitarian
Church,” will be constructed according to the design presented in this report. I understand that
the City of Fort Collins does not and will not assume liability for drainage facilities designed or
reviewed by my engineer. I also understand that the City of Fort Collins relies on the
representations of others to establish that drainage facilities are designed and built-in
compliance with applicable guidelines, standards or specifications. Review by the City of Fort
Collins can therefore in no way limit or diminish any liability which I or any other party may have
with respect to the design or construction of such facilities.”
(Owner/Applicant)
By: ____________________________________
Date:
3
Table of Contents
I. General Location and Description......................................................................................................... 4
A. Location ............................................................................................................................................. 4
B. Description of Property ..................................................................................................................... 4
II. Drainage Basin and Sub‐Basins ............................................................................................................. 5
A. Major Basin Description .................................................................................................................... 5
B. Sub‐Basin Description ....................................................................................................................... 5
III. Drainage Design Criteria ................................................................................................................... 6
A. Regulations ........................................................................................................................................ 6
B. Hydrological Criteria ......................................................................................................................... 6
C. Hydraulic Criteria .............................................................................................................................. 7
D. Waivers from Criteria ........................................................................................................................ 8
IV. Drainage Facility Design .................................................................................................................... 8
A. General Concepts .............................................................................................................................. 8
B. Specific Details .................................................................................................................................. 8
C. Stormwater Storage Facility .............................................................................................................. 9
V. Erosion and Sediment Control .............................................................................................................. 9
VI. Conclusions ..................................................................................................................................... 11
A. Compliance with Standards ............................................................................................................ 11
B. Drainage Concept ............................................................................................................................ 11
VII. References ...................................................................................................................................... 12
VIII. APPENDIX ........................................................................................................................................ 13
VICINTIY, FIRM & SOILS MAP
HYDROLOGICAL COMPUTATIONS
HYDRAULIC COMPUTATIONS
DRAINAGE DETAILS & PLANS
4
I. General Location and Description
A. Location
1. Township, Range, Section, ¼ Section: The subject property is located in Section
22, Township 7 North, Range 69 West of the 6th Principal Meridian, Larimer
County, State of Colorado.
2. Local streets within and adjacent to the development with ROW width shown:
The parcel is bordered by W. Drake Road to the south, Yorktown Drive to the
west, Yorktown Avenue to the north and Constitution Avenue to the east, see
Appendix A for Vicinity Map.
3. Major drainageways, facilities and easements within and adjacent to the site:
The site lies in the Spring Creek Drainage basin and crosses Drake Road
approximately 800 feet East of the Foothills Unitarian Church expansion (Site).
4. Names of surrounding developments: The existing church is located within a
residential area. There are existing single‐family residences located to the north,
west and east. The Georgetown Townhouse/Condos are located to the south.
B. Description of Property
1. Area in Acres: Property Area = 3.02 Acres
Tributary Pond Limits= 0.88 Acres
2. Ground cover: Ground cover on site currently consists of mature landscaping
which includes trees and shrubs along with established lawns.
3. National Resources Conversation Service (NRCS) soils classification: According
to the Natural Resources Conservation Service (NRCS) Soils Survey in Appendix A,
the project area is comprised mostly of soils in Hydrologic Soil Group B, which
consists of Altvan‐Satanta loam complex soil. Calculations for composite “C”
factors are included in Appendix B.
4. Major Drainageways: The Site lies within the Spring Creek Drainage Basin in the
reach East of Taft Hill Road as identified by the Spring Creek Drainageway
Planning Study.
5. Floodplain: According to the Flood Insurance Rate Map Panel No. 08069C0986G
dated 5/2/2012, the site is located with Zone X, an area of minimal flood hazard
(see Appendix)
6. General Project Description: The proposed Foothills Unitarian Church expansion
includes a new two‐story addition at the southwest edge of the existing building.
There will also be new pedestrian connection to the existing parking lot located
on the west, and to the existing sidewalk along Drake. In addition to the proposed
expansion; there will also be ROW improvements along Yorktown Drive and
Yorktown Avenue which consists of new curb, gutter and sidewalk.
5
7. Irrigation facilities: There are no known irrigation facilities within 200 feet of the
site.
8. Proposed Land Use: Place of worship
II. Drainage Basin and Sub‐Basins
A. Major Basin Description
1. On‐site and off‐site major drainage basin characteristic and flow patterns and
path: Historically the site drains into the surrounding road ROW and is tributary
to Drake Road.
2. Existing and proposed land uses within the basins if known: The existing
Foothills Unitarian Church will remain as a place of worship.
3. Discussion of all drainageway planning or floodplain delineation studies that
affect the major drainageways, such as FHAD Studies and Outfall System
Planning studies: There are no known drainageway planning or floodplain
delineation studies associated with the property.
4. Discussion of the condition of any channel within or adjacent to the
development, including existing conditions, need for improvements can impact
on the proposed development: Spring Creek is directly east of the proposed
development.
5. Discussion of the impacts of the off‐site flow patterns and paths, under fully
developed conditions: Currently flow from off‐site are captured with curb and
gutter and conveyed into the existing public storm sewer system within Drake
Road.
6. Identification of all irrigation facilities within the basin which will influence or
be influenced by the local drainage: There are no know irrigation facilities within
the basin which will influence or be influenced with the developed drainage
patterns.
B. Sub‐Basin Description
1. On‐site and off‐site minor drainage basin characteristics and flow patterns
under historic and developed conditions: Based on the Final Drainage Study &
Erosion Control Report – Foothills Unitarian Church Expansion dated April 3,
1996; the property contains 4 basins (A1–A4). The proposed expansion
completely encompasses basin A3. Historic Basin A3 flows are currently
conveyed via surface flow into Drake Road and will outfall into the public storm
sewer system in the existing inlet directly south of the proposed expansion area.
Basin A1 flows will remain unchanged with the proposed ROW improvements
along Yorktown Avenue, and outfall into the existing curb and gutter as it
currently does today. Basin A2 flow patterns will mimic historic and continue into
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Drake Road. Basin A4 flow patterns will also remain unchanged and be captured
within the western parking lot detention area prior to outfalling into Drake Road
and ultimately Spring Creek via the public storm sewer system, see Appendix for
drainage map.
With the proposed building expansion, developed basin P1 will analyze the
historic basin A3 to determine the required detention volumes based on the
added imperviousness to the site.
Basin P1 is approximately 0.88 acres with an imperviousness of 39%. This basin
consists of the area contained within historic Basin A3 and also includes additional
pervious areas that include the proposed detention pond. The 2‐yr runoff
coefficient is 0.28 and the 100‐yr runoff coefficient is 0.61.
2. Existing and proposed land uses within the basins: The site currently is a place
of worship with mature landscaping and associated parking and walkways. The
proposed development will consist of a building expansion, and the primary use
will remain the same.
3. Discussion of irrigation facilities that will influence or impacted by the site
drainage: There are no known existing irrigation facilities that will be impacted
by the proposed development.
4. Discussion of the impacts of the off‐site flow patterns and paths under fully
developed conditions: Under the fully developed conditions flows from within
the surrounding roadways will be captured with curb and gutter and ultimately
into Drake Road.
III. Drainage Design Criteria
A. Regulations
1. Discussion of the optional provisions selected or the deviation from the Criteria,
if any, and its justification: Calculation methods used follow the provisions set
forth in the Fort Collins Stormwater Criteria Manual and the Urban Storm
Drainage Criteria Manual.
B. Hydrological Criteria
1. Identify design rainfall: The property lies in Larimer County Rainfall Zone I. Storm
incremental precipitation determined by using the City of Fort Collins Table RA‐3.
2. Identify runoff calculation method: The Rational Method was used to determine
developed flow volumes for historic and developed conditions. The Rational
Formula is Q = CiA, where Q, the maximum rate of runoff is equal to the runoff
coefficient C, times the rainfall intensity (I), times the area (A).
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3. Identify detention discharge and storage calculation method: Water quality and
stormwater detention is proposed to be provided within a newly proposed
detention pond. The proposed pond was evaluated using the FAA method and
designed to hold the required 100‐yr storage volume including the WQCV for the
project. The required volume will be based on the additional impervious area. The
existing impervious areas have been “grandfathered” in and this runoff can be
passed through the pond. The required WQCV is 0.01 acre‐ft. the total required
100‐yr detention volume is 0.07 acre‐ft which includes the required WQCV.
4. Identify design storm recurrence intervals: Design storm recurrence intervals of
2 and 100‐year events were examined in this study
5. Discussion and justification or other criteria or calculation method used that are
not presented in or referenced by these the CRITERIA: All criteria and calculation
methods used are presented in or referenced by the Fort Collins Stormwater
Criteria Manual.
The allowable release rate and required volume for a minor redevelopment of an
existing site that has no detention, will be based on the following;
a) Calculation for allowable release rate
a. 100‐yr flows from existing impervious areas are grandfathered.
b. New impervious are require flows to be detained to the 2‐yr historic
flow rate.
c. Calculate the 100‐yr flow rate from all existing impervious areas onsite.
d. Calculate the 100‐yr flow rate for pervious areas that will remain as
pervious.
e. Calculate the 2‐yr release rate, for pervious areas to convert to
impervious. Assuming C‐factor = 0.2 for 0% impervious (historic).
f. Sum the flow rates calculated. This will be the max allowable release
rate for site.
b) Calculation for detention.
a. Calculate the free releases from site (100yr). Subtract from max
allowable release. This will be the maximum allowable release rate.
b. Perform FAA detention calculation using the "required detention
release rate" which will determine the required detention volume,
based on the mass balance method.
c. Use area and C factor for everything draining to the pond location.
C. Hydraulic Criteria
1. Identify various capacity references: The Urban Storm Drainage Criteria Manual,
Volumes 1‐3 and the Fort Collins Stormwater Criteria Manual were utilized in the
storm drainage design for the proposed development. See Appendix C for
hydraulics calculations of the storm sewer system for sizing details.
8
D. Waivers from Criteria
1. Provide justification for each waiver: No waivers are requested for the proposed
development.
IV. Drainage Facility Design
A. General Concepts
1. Discussion of concept and typical drainage patterns: The proposed Foothills
Unitarian Church expansion includes an addition at the southwest edge of the
existing building. There are no known drainage issues on the site with the
proposed expansion. Historically the drainage flows for the di sturbed area based
on basin A3 flows across the property in West Drake Road right of way.
The pre‐development flows for the site is approximately 0.20 CFS for the minor
event and 1.41 CFS for the major event. In the developed condition flows mimic
the historic flow patterns into the proposed water quality/detention pond at the
southeast portion of the site. The pond is will be fitted with an outlet structure
that will incorporate a water quality and 100‐yr orifice plates in order to have
flows released at the allowable rate.
Post‐development flows were determined to be 0.17 CFS and 1.36 CFS for the
minor and major event.
All drainage that occurs within the disturbance limits of basin P1 will be directed
into the detention pond by overland flow. Once in the pond, an outlet structure
will control release rates for both the water quality capture volume and 100‐yr
storm event, while an emergency spillway accounts for events greater than the
1‐hour, 100 yr storm.
2. Discussion of anticipated and proposed drainage patterns. Discuss how runoff
is conveyed off‐site to nearest adequate drainage facility. Discuss flow path and
downstream capacity: The flows from the proposed expansion will be conveyed
overland to the proposed detention pond. The outlet structure includes a 15‐inch
reinforced concrete pipe with a WQCV orifice plate and 100‐yr restrictor plate.
The emergency spillway will include a concrete cutoff wall. The 15‐inch outlet
pipe will tie into an existing storm inlet within West Drake Road right of way
B. Specific Details
1. Discussion of drainage problems encountered and solutions at specific design
points: There are no known drainage problems encountered and any design
points for the proposed development.
2. Discussion of detention storage and outlet design: The pond is designed per the
mass balance method in order to determine the required detention for
developments adding over 5000 sf of impervious areas. The pond is fitted with
an outlet structure that incorporates a water quality orifice along with a restrictor
plate on the outlet pipe that connects to the back of an existing storm inlet within
West Drake Road right of way.
9
C. Stormwater Storage Facility
1. Discuss detention pond designs, including release rates, storage volumes and
water surface elevations for the WQCV and emergency overflow conditions,
outlet structure design, emergency spillway design, etc: The proposed storm
drainage design for the expansion consists of a detention pond fitted with an
outlet structure that have controlled release with orifices. The property is
approximately 3.02 acres with 0.88 acres of area that will be tributary to the
proposed pond.
Required volumes are based on the total disturbed area of the property which is
0.88 acres at 39% imperviousness which results in a required WQCV of 0.01 acre‐
feet and a required 100‐year volume of 0.062 acre‐ft. The total required 100‐year
volume for the proposed development is 0.072 acre‐ft which includes WQCV.
The 15‐inch RCP outlet pipe invert is at 5064.50. The developed WQCV WSEL =
5065.25 and the 100‐year WSEL = 5066.75. The emergency spillway elevation is
set to 5066.75 and the top of pond elevation = 5067.35. The freeboard provide
is 0.6‐ feet. The 100‐year allowable release rate for the site is approximately 1.29
CFS. There will no off‐site flows that will not be detained in the detention pond,
therefore there will be no reduction in the allowable release rate. The location
of the pond is ideal for events greater than the 100‐year event due to its close
proximity to the existing storm inlet within West Drake Road.
2. Discuss pond outfall locations and design, including method of energy
dissipation: The pond outfall is located at the south end property where it ties
into the back of an existing inlet within West Drake Road right of way. A 10‐foot
emergency spillway line which incorporates a 26‐foot head line with soiled rip rap
are to be part of the spillway design.
3. Discuss how runoff is conveyed from all pond outfalls and emergency spillways
to the nearest major drainageway, including a discussion of the flow path and
capacity downstream of the outfall to the nearest major drainageway: Runoff
from the proposed expansion will be conveyed into an existing storm inlet within
West Drake Road Road right of way, where it ultimately outfalls into Spring Creek,
directly east of the site. Based on the current historic flows and the allowable
release rate into the creek, there is no negative impacts of the flows from the
development into the creek.
V. Erosion and Sediment Control
A. General Erosion and Sediment Control Measures:
1. Minimizing Soil Exposure: When practical, the construction area and duration of
soil exposure should be kept to a minimum. All other areas should have a good
cover of vegetation of mulch. Grading should be completed as soon as possible
after commencement. revegetation will consist of seeding and erosion control
blankets.
10
2. Controlled Runoff Across Exposed Areas: When practical construction may
include construction temporary swales to intercept and direct storm water
around exposed areas.
3. Sediment Control: Temporary and/or permanent sediment control devices may
be installed to intercept and trap sediments.
B. BMP Selection:
1. General: UDFCD has long recommended a four‐step process for receiving
water protection that focuses on reducing runoff volumes, treating WQCV,
stabilizing streams and implementing long‐term source controls. The Four Step
Process pertains to management of smaller, frequently occurring events, as
opposed to larger storms for which drainage and flood control infrastructure
are sized. Implementation of these four steps helps to achieve compliance with
stormwater permit requirements (i.e. City’s MS4 permit). Added benefits of
implementing the complete process can include improved site aesthetics
through functional landscaping amenities that also provide stormwater quality
benefits.
2. Site BMPs: Due to the parameters of the proposed expansion and limited
disturbance, a grass swale will be utilized as a permanent BMP Runoff will be
conveyed overland into the proposed grass swale prior to outfalling into the
detention pond.
3. Erosion Control Plan: The summary of erosion control measures consists of
the following;
a) Installation of silt fences along West Drake Road.
b) Installation of inlet protections to the inlets within West Drake Road.
c) Installation of rock socks on the curb and gutter around the property.
d) Installation of seeding to all disturbed areas within the property.
e) Installation of erosion control blankets for areas of final grades that are
3:1 or steeper.
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VI. Conclusions
A. Compliance with Standards
1. Criteria: To the best of my knowledge, the drainage design set forth in the plans
and specifications complies with the Fort Collins Stormwater Criteria Manual.
2. Major Drainageway Planning Studies: To the best of my knowledge, the drainage
design set forth in the plans and specifications complies with any Planning
Studies.
3. Manual: To the best of my knowledge, the drainage design set forth in the plans
and specifications complies with the Fort Collins Stormwater Criteria Manual.
B. Drainage Concept
1. Effectiveness of drainage design to control damage from storm runoff: The
proposed design provides two permanent BMPs by means of a grass swale and
water quality/detention basin to promote infiltration for the proposed
development will provide the required volumes set forth by Fort Collins
standards.
2. Influence of proposed development of the Major Drainageway Planning Studies
recommendations(s): Current historic drainage patterns will be maintained and
an emergency overflow route from water quality/detention pond will convey
flows into West Drake Road right of way as it currently does today. There will be
no negative impacts downstream due to the runoff from the proposed
development.
12
VII. References
1. Urban Storm Drainage Criteria Manual, Volumes 1‐3; Mile High Flood District,
Denver, CO.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, December, 2018.
3. Final Drainage Study and Erosion Control Report‐ Foothills Unitarian Church
Expansion, Landmark Engineering, Loveland, CO, April 3, 1996.
VIII. APPENDIX
A. VICINTIY, FIRM & SOILS MAP
W. DRAKE ROAD
S. TAFT HILL ROAD
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOOD
HAZARD AREAS
Without Base Flood Elevation (BFE)
Zone A, V, A99
With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areas
of 1% annual chance flood with average
depth less than one foot or with drainage
areas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard information is derived directly from the
authoritative NFHL web services provided by FEMA. This map
was exported on 6/3/2021 at 10:46 AM and does not
reflect changes or amendments subsequent to this date and
time. The NFHL and effective information may change or
become superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximate
point selected by the user and does not represent
an authoritative property location.
1:6,000
105°6'56"W 40°33'26"N
105°6'18"W 40°32'58"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
FOOTHILLS UNITARIAN CHURCH
Natural
Resources
Conservation
Service
June 3, 2021
9
Custom Soil Resource Report
Soil Map
44891324489141448915044891594489168448917744891864489132448914144891504489159448916844891774489186490621 490630 490639 490648 490657 490666 490675 490684 490693 490702
490621 490630 490639 490648 490657 490666 490675 490684 490693 490702
40° 33' 12'' N 105° 6' 38'' W40° 33' 12'' N105° 6' 35'' W40° 33' 10'' N
105° 6' 38'' W40° 33' 10'' N
105° 6' 35'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 15 30 60 90
Feet
0 5 10 20 30
Meters
Map Scale: 1:385 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 15, Jun 9, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0 to 3
percent slopes
0.4 97.8%
4 Altvan-Satanta loams, 3 to 9
percent slopes
0.0 2.2%
Totals for Area of Interest 0.4 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
Custom Soil Resource Report
11
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
12
Larimer County Area, Colorado
3—Altvan-Satanta loams, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpw2
Elevation: 5,200 to 6,200 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Altvan and similar soils:45 percent
Satanta and similar soils:30 percent
Minor components:25 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Altvan
Setting
Landform:Benches, terraces
Landform position (three-dimensional):Side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 10 inches: loam
H2 - 10 to 18 inches: clay loam, loam, sandy clay loam
H2 - 10 to 18 inches: loam, fine sandy loam, silt loam
H2 - 10 to 18 inches: gravelly sand, gravelly coarse sand, coarse sand
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Available water capacity:Very high (about 13.2 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Custom Soil Resource Report
13
Hydrologic Soil Group: B
Hydric soil rating: No
Description of Satanta
Setting
Landform:Terraces, structural benches
Landform position (three-dimensional):Side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 18 inches: loam, clay loam, sandy clay loam
H2 - 9 to 18 inches: loam, clay loam, fine sandy loam
H2 - 9 to 18 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Available water capacity:Very high (about 27.4 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:10 percent
Hydric soil rating: No
Larim
Percent of map unit:10 percent
Hydric soil rating: No
Stoneham
Percent of map unit:5 percent
Hydric soil rating: No
Custom Soil Resource Report
14
4—Altvan-Satanta loams, 3 to 9 percent slopes
Map Unit Setting
National map unit symbol: jpwf
Elevation: 5,200 to 6,200 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Altvan and similar soils:55 percent
Satanta and similar soils:35 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Altvan
Setting
Landform:Fans, benches, terraces
Landform position (three-dimensional):Base slope, side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 16 inches: clay loam, loam, sandy clay loam
H2 - 9 to 16 inches: loam, fine sandy loam, silt loam
H2 - 9 to 16 inches: gravelly sand, gravelly coarse sand, coarse sand
H3 - 16 to 31 inches:
H3 - 16 to 31 inches:
H3 - 16 to 31 inches:
H4 - 31 to 60 inches:
H4 - 31 to 60 inches:
H4 - 31 to 60 inches:
Properties and qualities
Slope:6 to 9 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Custom Soil Resource Report
15
Available water capacity:Very high (about 13.7 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: B
Hydric soil rating: No
Description of Satanta
Setting
Landform:Structural benches, terraces
Landform position (three-dimensional):Side slope, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 14 inches: loam, clay loam, sandy clay loam
H2 - 9 to 14 inches: loam, clay loam, fine sandy loam
H2 - 9 to 14 inches:
H3 - 14 to 60 inches:
H3 - 14 to 60 inches:
H3 - 14 to 60 inches:
Properties and qualities
Slope:3 to 6 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Available water capacity:Very high (about 27.4 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Hydric soil rating: No
Minor Components
Nunn
Percent of map unit:6 percent
Hydric soil rating: No
Larimer
Percent of map unit:4 percent
Hydric soil rating: No
Custom Soil Resource Report
16
B. HYDROLOGICAL COMPUTATIONS
= FORMULA CELLS
= USER INPUT CELLS
PROJECT:
JOB NO.:
CALC. BY: ▼
DATE:
▼▼
Minutes
5
10
20
30
40
50
60
120
Equation 5-1 I=(28.5*P1)/(10+Td)^0.786
I = rainfall intensity (inches per hour)
P1 = 1-hour point rainfall depth (inches)
Td = storm duration (minutes)
Reference:
1) Urban Drainage and Flood Control District - Urban Storm Drainage Criteria Manual Volume 1, 2017
2) NOAA Atlas 14, Volume 8, Version 2
http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=co
0.660.19
1.07
IDF Rainfall Data
2-Year
Minor Storm Major Storm
Td 100-Year
Foothills Unitarian Church
CO3355
LTV
6/23/2021
1.02
0.81
0.59
0.47
0.39
0.34
0.30
User Input
Project Location
P1: 1-hour Rainfall Depths (inches)
0.30 1.06
3.60
2.87
2.09
1.66
1.40
1.21
Baseline Engineering,
Planning and Surveying
6/23/2021
CO3355_SF2 SF3-Revised 2017 Standards
PROJECT:
JOB NO.:
CALC. BY:
DATE:
Impervious Percentages - from Urban Drainage Table 6-3
Paved 100% 0
Roofs 90% 0
Lawns, sandy soil 2% 0
Historic flow analysis I 2% 0
SOIL TYPE:B (use equation from Table 6-4)= FORMULA CELLS
= USER INPUT CELLS
Basin Area (ac) Imp.C2 C5 C10 C100 Paved Roofs
Lawns, sandy
soil
Historic flow
analysis I Land Use Land Use Land Use Land Use
A3-1 0.233 100% 0.84 0.86 0.87 0.90 0.23
Basin Area (ac) Imp.C2 C5 C10 C100 Paved Roofs
Lawns, sandy
soil
Historic flow
analysis I Land Use Land Use Land Use Land Use
A3-2 0.518 2% 0.01 0.01 0.07 0.44 0.52
Basin Area (ac) Imp.
C2 C5 C10 C100 Paved Roofs
Lawns, sandy
soil
Historic flow
analysis I Land Use Land Use Land Use Land Use
A3-3 0.123 2% 0.01 0.01 0.07 0.44 0.12
Basin Area (ac) Imp.
C2 C5 C10 C100 Paved Roofs
Lawns, sandy
soil 0.00 0.00 C10 0.07 0.00
P1 0.882 39% 0.28 0.31 0.37 0.61 0.03 0.34 0.52
Areas (ac)
Land Use
Land Use
Land Use
Land Use
Foothills Unitarian Church
CO3355
LTV
6/23/2021
EXISTING IMPERVIOUS AREAS
Weighted Impervious and C Values
Areas (ac)Weighted Impervious and C Values
Weighted Impervious and C Values Areas (ac)
EXISTING PERVIOUS AREAS TO REMAIN PERVIOUS AREAS
EXISTING PERVIOUS AREAS TO CHANGE TO IMPERVIOUS AREAS
DEVELOPED CONDITIONS
Weighted Impervious and C Values Areas (ac)
Baseline Engineering,
Planning and Surveying COMPOSITE C VALUES - PROP
6/23/2021
CO3355_SF2 SF3-Revised 2017 Standards
Project: Foothills Unitarian ChurchJob No.: CO3355Calculated By: Checked By: xxxxxxxxxxDate: FINAL REMARKStcBasin iC5AREA LENGTH SLOPEtiLENGTH SLOPE VEL.ttCOMP. TOT. LENGTHSoAc Ft % Min Ft % FPS MintcFt % Min Min(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)A3-1 1.00 0.86 0.23 76 2.0 3.01 165 7 6.1 1.73 1.59 4.6 241 4.81 9.8 5.00A3-2 0.02 0.01 0.52 76 2.0 13.62 165 7 6.1 1.6 1.7 15.3 241 4.81 27.6 15.3A3-3 0.02 0.01 0.12 76 2.0 13.62 165 7 6.1 1.6 1.7 15.3 241 4.81 27.6 15.3P1 0.39 0.31 0.88 90 2.0 10.83 265 7 6.6 1.7 2.6 13.4 355 5.43 21.2 13.4Equation 6-3ti=((0.395(1.1-C5)SQRT(L))/(So^0.33))Equation 6-5tc=(26-17i)+(Lt/(60(14i+9)SQRT(So)))= FORMULA CELLS= USER INPUT CELLSDEVELOPED CONDITIONStc (Equation 6-5)TIME OF CONCENTRATION SUMMARYtc CHECK(URBANIZED BASINS)TRAVEL TIME(tt)CvEXISTING IMPERVIOUS AREASEXISTING PERVIOUS AREAS TO REMAIN PERVIOUS AREASEXISTING PERVIOUS AREAS TO CHANGE TO IMPERVIOUS AREASSTANDARD FORM SF-2INITIAL/OVERLANDTIME (ti)LTVDATASUB-BASIN6/23/2021NRCS Conveyance Factor K Table - Cv Value20Paved Areas and Shallow Paved SwalesShort Pasture and LawnsNearly Bare GroundGrassed Waterway71015Heavy Meadow 2.5Tillage/Field 5Baseline Engineering,Planning and SurveyingTOC6/23/2021CO3355_SF2 SF3-Revised 2017 Standards
Calculated By: Project: Foothills Unitarian ChurchDate: Job No.: CO3355Checked By: Design Storm: 2-Year= FORMULA CELLS= USER INPUT CELLSDESIGN POINTAREA DESIGNAREA (AC)RUNOFF COEFF tc (MIN)C * A (AC)I (IN/HR)Q (CFS)tc (MIN)S (C * A) (CA)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOWDESIGN FLOW (CFS)SLOPE (%)PIPE DIAM. (IN.) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)A3-1 0.23 0.84 5.0 0.20 1.020.199A3-2 0.52 0.01 15.3 0.00 0.670.003A3-3 0.12 0.01 15.3 0.00 0.670.001Used to determine max allowable release rateP1 0.88 0.28 13.4 0.24 0.720.174Used as allowable release rate for WQCVREMARKSBASINDIRECT RUNOFF TOTAL RUNOFF STREET PIPELENGTH (FT)2-Year0.301-hour rainfall=VELOCITY (FPS)tt (MIN)STANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)LTV6/23/2021xxxxxxxxxxBaseline Engineering,Planning and SurveyingMinor SF-36/23/2021CO3355_SF2 SF3-Revised 2017 Standards
Calculated By: Project: Foothills Unitarian ChurchDate: Job No.: CO3355Checked By: Design Storm: 100-Year= FORMULA CELLS= USER INPUT CELLSDESIGN POINTAREA DESIGNAREA (AC)RUNOFF COEFF tc (MIN)C * A (AC)I (IN/HR)Q (CFS)tc (MIN)S (C * A) (CA)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOWDESIGN FLOW (CFS)SLOPE (%)PIPE DIAM. (IN.) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)A3-1 0.23 0.90 5.0 0.21 3.600.749Used to determine max allowable release rateA3-2 0.52 0.44 15.3 0.23 2.380.537Used to determine max allowable release rateA3-3 0.12 0.44 15.3 0.05 2.380.127P1 0.88 0.61 13.4 0.54 2.531.356LENGTH (FT)VELOCITY (FPS)tt (MIN)REMARKSDIRECT RUNOFF TOTAL RUNOFF STREETLTVSTANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)BASINPIPE6/23/2021xxxxxxxxxx1.06100-Year 1-hour rainfall=Baseline Engineering,Planning and SurveyingMajor SF-36/23/2021CO3355_SF2 SF3-Revised 2017 Standards
C. HYDRAULIC COMPUTATIONS
Project: Foothills Unitarian Church
Job No.: CO3355
Calculated By: Checked By: xxxxxxxxxx
Date:
BASIN
Q2YR
(CFS)
Q100YR
(CFS)
A3-1 0.199 0.749
A3-2 0.003 0.537
A3-3 0.001 0.127
1.287
BASIN
Q2YR
(CFS)
Q100YR
(CFS)
P1 0.174 1.356
-00
1.287 CFS
DESCRIPTION
Flow rate from developed conditions
Free release flows off-site
Required Detention Release Rate=
Flow rate from all existing impervious areas
Flow rate for pervious ares to remain pervious areas
Flow rate for pervious ares to convert to imperviousnes areas
Used to determine max allowable release rate for the site
Max Allowable Release Rate =
DEVELOPED CONDITIONS
DESCRIPTION
Flow Summary
LTV
6/23/2021
EXISTING CONDITIONS
Baseline Engineering,
Planning and Surveying Flow Summary
6/23/2021
CO3355_SF2 SF3-Revised 2017 Standards
Water Quality Capture Volume, WQCV 1. Determine the WQCV in Watershed Inches WQCV = a(0.91I3‐1.19I2+0.78I)Where: WQCV = Water Quality Capture Volume, watershed inchesa =coefficient corresponding to WQCV drain timeI = Imperviousness (%/100)Drain Time (hrs)Coefficient (a)12 0.824 0.940 1.0Coefficient, a 0.80Imperviousness, I 39WQCV = 0.14watershed inches2. Determine the required storage volume in Acre‐FeetV = (WQCV/12)AWhere:V = Required Storage Volume, acre‐feetA = Tributary catchment area upstream, acresArea, A 0.882 acresV = 0.0104acre‐feetV = 451cubic‐feetDrain Time CoefficientsUSED TO DETERMINE WQCVBASED ON UDFCD CRITERIA.
0.611.251.287 CFS0.882 ACRESResults0.0723129Rainfall Duration (min)Rainfall Intensity (in/hr)Qin (cfs)Volumein (ft3)Qout (cfs)Volumeout (ft3)Volume detained (acre‐feet)5 9.966.67 2000.40 1.29 386.23 0.03710 7.745.18 3109.05 1.29 772.46 0.05415 6.524.36 3928.49 1.29 1158.69 0.06420 5.613.76 4506.92 1.29 1544.92 0.06825 4.973.33 4988.95 1.29 1931.15 0.07030 4.523.03 5446.87 1.29 2317.38 0.07235 4.082.73 5736.08 1.29 2703.61 0.07040 3.742.50 6001.19 1.29 3089.83 0.06745 3.452.31 6242.21 1.29 3476.06 0.06450 3.232.16 6483.22 1.29 3862.29 0.06055 3.032.03 6700.13 1.29 4248.52 0.05660 2.861.91 6892.94 1.29 4634.75 0.05265 2.711.82 7085.75 1.29 5020.98 0.04770 2.591.73 7278.56 1.29 5407.21 0.04375 2.481.66 7471.37 1.29 5793.44 0.03980 2.381.59 7640.08 1.29 6179.67 0.03485 2.291.53 7808.78 1.29 6565.90 0.02990 2.211.48 7977.49 1.29 6952.13 0.02495 2.131.42 8122.10 1.29 7338.36 0.018100 2.061.38 8290.81 1.29 7724.59 0.013105 2.001.34 8435.41 1.29 8110.82 0.007110 1.941.30 8580.02 1.29 8497.05 0.002115 1.881.26 8700.53 1.29 8883.27 ‐0.004120 1.841.23 8845.13 1.29 9269.50 ‐0.010Detention Volume Requirement (cubic‐feet)Detention Volume Requirement (acre‐feet)Detention Volume ‐ Mass Balance MethodAdditional Detention for Development Adding Over 5000 SQFT of Impervious AreaRunoff Coefficient, C =Frequency Factor, Cf =Max Release, Qout =Area = USED TO DETERMINE THE ADDITIONAL REQUIRED VOLUME BASED ON FORT COLLINS INCREASED IMPERVIOUS CRITERIA.
Project: Foothills Unitarian Church
Job No.: CO3355
Calculated By: LTV Checked By: xxxxxxxxxx
Date: 6/23/2021
DESIGN EVENT
TOTAL AREA
(ACRES)
WQCV 0.88
100 YR DETENTION 0.88
REQUIRED VOLUME SUMMARY
REQUIRED
VOLUME
(ACRE-FT)
0.010
0.072
PERCENT
IMPERVIOUS
REQUIRED
VOLUME
(FT3)
53.00% 451
53.00% 3129
Baseline Engineering,
Planning and Surveying VOLUME SUMMARY
6/23/2021
CO3355_Fort Collins Rational Method Spreadsheet
PROJECT : PROJECT LOCATION: Fort Collins DATE :
PROJECT NO. :BY :
Provided Volume
Stage (ft)
Contour
Elevation
(ft)
0.00 5064.75
0.25 5065.00
1.25 5066.00
2.25 5067.00
2.60 5067.35
WQCV =5065.25 0.50 1,253.00 452.54 0.010
EURV =
2‐yr =
5‐yr =
10‐yr =
100‐yr =5066.75 2.00 2,273.00 3,197.92 0.073
= FORMULA CELLS
= USER INPUT CELLS
WSEL Depth (ft)
Area
(ft2)
Volume
(ft3)
Volume
(ac‐ft)
6/23/2021
LTV
Foothills Unitarian
CO3355
Area
(ft2)
0
1,000
2,012
2,360
83
1,477
2,184
1,014.03,470
0.0
83
1,560
3,744
4,757.9
1/3 (A1 + A2 +
(A1A2)1/2) D
Total Volume
(ft3)
Total Volume (ac-
ft)
0.000
0.002
0.036
0.086
0.109
Extended Detention Basin
Outlet Structure Orifice Sizing
1. 100‐yr Orifice (using orifice equation)
a. Use Orifice Equation to solve for orifice diamter
Q =CoA√2gh
Where:
Q = flow rate or allowable discharge, cfs
Co =orifice coefficient, typically 0.61
A =cross‐sectional area, ft2
g =gravitational constant, 32.2 ft/sec2
h = water surface elevation minus elevation of centroid of orifice, ft
Q = 1.29 cfs
Co =0.61 dimensionless
h = 2.00 ft
A = 0.186 ft2
orifice diameter = 5.84 inches
USE =5.75 inches
2. WQCV Perforated Orifice
a. Determine the required area per row of orifices
a =
0.013DWQ
2 + 0.22DWQ
‐0.10
Where:
Ao = Area per row of orifices spaced on 4" centers, in2
WQCV = Water Quality Capture Volume or "Volume", acre‐ft
DWQ = Depth of volume, ft
V = 0.010 acre‐ft
DWQ = 0.50 ft
a = 0.043 in2 per row or from Figure EDB‐3
b. Determine diameter of circular perforations
A0 = 0.049 in2 per row
Diameter = 0.250 inches
WQCV
c. Determine number of columns
Number of Columns = 1 from Table 6a‐1
d. Round Orifice Diameter to nearest 1/16 inch
Area per Perforation = 0.049 in2
Diameter per Perforation = 0.250 inches
Actual Perforation Diameter = 1/4 inches user input (round to nearest 1/16th inch)
Actual Area per Perforation = 0.049 in2
Actual Area per Row = 0.049 in2 per row
Minimum Steel Plate Thickness = 1/4 inches from Figure 5
0.0625 1/16
0.1250 1/8
0.1875 3/16
0.2500 1/4
0.3125 5/16
0.3750 3/8
0.4375 7/16
0.5000 1/2
0.5625 9/16
0.6250 5/8
0.6875 11/16
0.7500 3/4
0.8125 13/16
0.8750 7/8
0.9375 15/16
1.0000 1
e. Trach Rack Opening Width
Max Diameter of Perforations = 0.250 inches
DWQ = 2.00 ft
h of Trash Rack per Column of Holes = 3 inches user input from Table 6a‐1
Total Trash Rack Opening Width = 3 inches
Total Trash Rack Height = 26 inches
Trash Rack Design Specs = use Table 6a‐2
Diameter Conversion from decimal to architectural
This unofficial copy was downloaded on Jun-18-2021 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
D. DRAINAGE DETAILS & PLANS
T
Know what's below.
before you dig.CallR
DEVELOPED RUNOFF SUMMARY
BASIN
ID
DESIGN
POINT
AREA
(ACRES)
TC
(MIN)IMPERVIOUSNESS C2 C100 Q2
(CFS)
Q100
(CFS)
T
Know what's below.
before you dig.CallR
Know what's below.
before you dig.CallR